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Presenter Greg Foot investigates the urban myth that if the whole population of the world jumped at the same time, it could cause an earthquake big enough to affect the speed at which the Earth turns on its axis. He starts by looking at data which showed that a Japanese earthquake that measured 8.9 on the Richter scale and caused the rotation of the Earth to speed up by 2 metres per day. To produce his data he asks 50,000 people at the Reading festival to jump at the same time. This causes an earthquake that measures 0.6 on the Richter scale. Greg then calculates that if the whole population of the Earth, i.e 6.9 billion people jumped up and down at the same time, it would still be a factor of seven million short of altering the speed at which the Earth rotates.
First broadcast:
4 March 2012

Classroom Ideas

Students can investigate the effect of the conservation of angular momentum by looking at clips of ice skaters spinning with arms held out and how spin increases when they draw their arms in. There are clear cross-curricular links with Geography and Geology concerning earthquakes and with astronomy on how angular momentum is conserved in spinning neutron stars and black holes.